Pre-mixing type gas burner



y 14, 1970 lSAMU MATSUDA FEE-MIXING TYPE GAS BURNER 2 Sheets-Sheet 1 Filed 00 15, 1968 FIG.I

FIGS

FIGZ

INVENTOR ISAMU MATSUDA MwrV /%Z 7 I ATTORNEYS July 14, 1970 ISAMU MATSUDA FEE-MIXING TYPE GAS BURNER 2 Sheets-$heet 2 Filed Oct. 15, 1968 BURNER $125 I INCHES O O O O O 5 3 mo 22V mmzmzm mom; mmnwmw 50 FLOW RATE NM /RR) INVENT OR ISAMU MATSUDA BY 57W ATTORNEYS United States Patent PRE-MIXIN G TYPE GAS BURNER Isamu Matsllda, Tokyo, Japan, assignor to Tokyo Gas Company Limited, Tokyo, Japan Filed Oct. 15, 1968, Ser. No. 767,699 Claims priority, application Japan, May 16, 1968, 43/ 32,551 Int. Cl. F23c 7/00 US. Cl. 431-187 2 Claims ABSTRACT OF THE DISCLOSURE A pre-mixing type gas burner. A central air flow tube with a closed tip and an air inlet at the end opposite the tip has a gas flow pipe coaxial with and surrounding it and spaced therefrom to define a gas flow region therebetween. The gas flow pipe is open at the tip end and extends beyond the tip end of the air flow tube and is attached to the air inlet end of the air flow tube so as to close off the end of the gas flow pipe. A gas inlet pipe opens into the air inlet end of the gas flow pipe. Secondary air outlet tubes extend from Within the air flow tube outwardly through the gas flow pipe at a point spaced toward the air inlet end of the burner from the tip of the burner. Said air flow tube has primary air nozzles opening radially outwardly thereof just behind the tip and has air ports opening outwardly into said flow space just ahead of said air inlet. The burner is mounted in a furnace wall burner opening spaced from the walls of the opening to form a secondary air flow space around said gas flow pipe. When gas and air are caused to flow through said burner, a high temperature fluid recirculation zone is formed in front of the tip of said burner to keep the fuel burning and secondary air flows along the outside of the gas flow pipe and cools the pipe and stabilizes the burning gases.

This invention relates to a gas burner so constructed that a high temperature fluid recirculation zone is pr0- vided at the tip and a portion of the combustion air is introduced around the periphery of the gas flow region for cooling and achieving the effect of secondary combustion air, thereby to ensure the stability of flame and prevent overheating of the burner pipe.

Generally, gas burners have been classified into two groups, according to the type of gas-air mixing method used therein, i.e., premixing types and nozzle-mixing types. The former type has the drawback that there is a danger of flash back, While the latter has the drawback that there is frequent blow out because of the smaller combustion capacity.

It is an object of the present invention to provide a pre-mixing type of gas burner in which blow out is completely prevented. The object of this invention is achieved by the provision of a burner with a high temperature fluid recirculation zone at the tip of the burner and by providing for continuous ignition of the gaseous mixture. The burner according to the present invention has a construction wherein a high temperature fluid recirculation zone is provided in the vicinity of the tip of an air flow region which is formed by air from primary air nozzles directed perpendicularly to the gas flow, and a secondary air flow region is formed around the gas flow region for introducing secondary air from secondary air tubes formed at the other end of the air flow region.

The invention will now be more fully described with reference to the accompanying drawings showing an embodiment thereof, and in which:

FIG. 1 is a diagrammatic longitudinal section of the gas burner according to the invention;

Town gas" FIG. 2 is a partially enlarged sectional view of the tip of the burner;

FIG. 3 is a cross-sectional view taken on line 33 of FIG. 1; and

FIG. 4 is a graph showing the results of tests conducted on a burner in accordance with the invention.

In the drawings, an air flow tube 1 is provided having a closed tip 1a and an air inlet 2 at the end thereof remote from the tip. Around this air flow tube 1 is a gas flow pipe 6 which is open at the tip end and attached to the air flow tube at the air inlet end and which has a gas inlet pipe 4 opening into pipe 6 at the air inlet end. Pipe 6 is spaced from air flow tube 1 to define a gas flow space 3 therebetween. A plurality of primary air nozzles 5 are provided in the tip end of air flow tube 1 and extend perpendicularly to the axis of the gas flow tube 1. The gas flow pipe 6 extends beyond the tip of air flow tube 1 and defines with the tip of the air flow tube 1 a high temperature fluid recirculation zone 7 in front of said tip. By the term high temperature fluid recirculation zone is meant the zone of the vortex indicated by the arrows in FIG. 2. Here a high temperature burning gas flows in a vortex continuously igniting the outflowing mixture of gas and air to avoid the blow out, or to form a buffer effect, in a sense. Around the gas flow space 3 and gas flow tube 6 is formed a secondary air flow region 8 defined between the gas flow tube 6 and the burner bore in wall 11 of the furnace. Air is introduced thereinto through secondary air outlet tubes 9 extending outwardly through the air flow tube 1 just ahead of air inlet 2 admit air to be mixed ondary air at the tip zone 10 beyond the end of the gas tube 6 and, at the same time, it cools the burner pipe 6 to prevent overheating. Air ports 12 formed in the air flow tube 1 just ahead of air inlet 2 admit air to be mixed with gaseous fuel which is fed in through gas inlet pipe 4. The size and shape of the air ports 12 can be designed, as will be described later, to best suit the particular gaseous fuel to be employed.

In a burner of the construction described above, air is introduced from the air inlet 2 and a gaseous fuel from the gas inlet pipe 4. The gaseous fuel, after having some air mixed therewith from ports 12, passes through the gas flow region 3 and burns when rapidly mixed with primary air which jets out through the primary air nozzles 5 provided in one end of the air flow tube 1 perpendicularly to the flow of the gas-air mixture. This produces a high temperature fluid recirculation zone as indicated by the arrows in FIG. 2. In this way, the gaseous mixture is continuously ignited and blow out is completely avoided. In the mean time, part of the air from air flow tube 1 flows through the secondary air tubes 9 into the secondary air flow region 8, and serves as secondary air in the tip zone 10 to stabilize the flame and cool the burner pipe 6.

As for the size or total cross-sectional area of the air ports .12, the following ratios with respect to the other air ports are suitable, for example, for the respective gaseous fuels as given below:

Primary air nozzles (5) h t-Hi Upon being tested, the burners constructed in accordance with the invention had very good burning characteristics, and produced no flash back or blow out which are inherent in conventional burners. Furthermore, the burners of the invention when used in a furnace at 1800 C. required no special cooling means such as is indispensable for ordinary burners used at such temperatures.

The construction of the present invention as described above achieves first the effect of promoting the mixing of primary air with the gaseous fuel by the provision of air jets through nozzles 5 directed perpendicularly across the flow of the gas, and precludes any possibility of blow out by creating the vortex of burned gas in the high temperature fluid recirculation zone, and thereby ensuring continuous ignition. In addition, secondary air passed through the secondary air flow region joins the burning gas in front of the tip of the zone so as to combine with the aforesaid effects to stabilize the flame and also to cool the burner pipe. Since the burner is protected against overheating in this 'way, it needs no cooling means as required by ordinary burners, and therefore it can be made of metals, which are easily fabricated and have great structural strength. A further advantage of the invention is the possibility of using low pressure gases and air with the burner because the structure of the burner causes no pressure drop in the course of operation.

In FIG. 3 there are shown typical flow curves for burners of different sizes according to the invention. Also, through choice of the size of air ports 12 according to the type of gaseous fuel to be used, a single burner of the invention can have universal applications.

What is claimed is:

1. A gas burner installation comprising a gas burner having a central air flow tube with a closed tip and an air inlet at the end opposite the tip, a gas flow pipe coaxial with and surrounding the air flow tube and spaced therefrom to define a gas flow region therebetween and which is open at the tip end and extends beyond the tip end of the air flow tube and is attached to the air inlet end of the air flow tube so as to close off the end of the gas flow pipe, a gas inlet pipe opening into the air inlet end of the gas flow pipe, secondary air outlet tubes extending from within the air flow tube outwardly through the gas flow pipe at a point spaced toward the air inlet end of the burner from the tip of the burner, and said air flow tube having primary air nozzles opening radially outwardly thereof just behind the tip and having air ports opening outwardly into said gas flow space just ahead of said air inlet, said installation further comprising a furnace wall having a burner opening therein in which said burner is mounted spaced from the Walls of the opening to form a secondary air fiow space around said gas flow pipe, whereby when gas and air are caused to flow through said burner a high temperature fluid recirculation zone is formed in front of the tip of said burner to keep the fuel burning and secondary air flows along the outside of the gas flow pipe and cools the pipe and stabilizes the burning gases.

2. A gas burner for installation in a burner opening in a furnace wall, said gas burner comprising a central air flow tube with a closed tip and an air inlet at the end opposite the tip, a gas flow pipe coaxial with and surrounding the air flow tube and spaced therefrom to define a gas flQ'W region therebetween and which is open at the tip end and extends beyond the tip end of the air flow tube and is attached to the air inlet end of the air flow tube so as to close otf the end of the gas flow pipe, a gas inlet pipe opening into the air inlet end of the gas flow pipe, secondary air outlet tubes extending from within the air flow tube outwardly through the gas flow pipe at a point spaced toward the air inlet end of the burner from the tip of the burner, and said air flow tube having primary air nozzles opening radially outwardly thereof just behind the tip and having air ports opening outwardly into said gas flow space just ahead of said air inlet, said burner being adapted to be mounted in the burner opening spaced from the walls of the opening to form a secondary air flow space around said gas :flow pipe, whereby when gas and air are caused to flow through said burner, a high temperature fluid recirculation zone is formed in front of the tip of said burner to keep the fuel burning and secondary air flows along the outside of the gas flow pipe and cools the pipe and stabilizes the burning gases.

References Cited UNITED STATES PATENTS 1,006,324 10/ 1911 Werner 431-353 2,806,516 9/1957 Brola 43 l352 X 3,119,439 1/1964 Weiss 431353 X CARROLL B. DORITY, JR., Primary Examiner U.S. c1. X.R. 431451 '3 

